all: update golang.org/x dependencies

Updating to a newer x/tools version teaches it about export data
version 3, and in turn fixes test failures that happen at Go tip:

$ go version
go version go1.27-devel_edc5480072 Wed May 6 07:53:10 2026 -0700 darwin/arm64
$ go test ./...
[...] failed: can't fix source: [...] cannot decode "google.golang.org/open2opaque/internal/fix/testdata/proto2test_go_proto", export data version 3 is greater than maximum supported version 2 [...]

For golang/go#9859.
Fixes golang/open2opaque#23.

[git-generate]
go get golang.org/x/{tools,sync,exp}
go mod tidy

PiperOrigin-RevId: 911792924
Change-Id: I95e7172bce61de64ae338a419eb3eac452fb55db